The present invention relates to a method and apparatus for staking together two optical elements in order to retain their alignment.
Many optical systems are fabricated in several pieces and must be assembled prior to use. In addition, these optical systems often involve two or more components which must be aligned to within a fraction of a wavelength of light. This alignment must be maintained during and after assembly of the optical components.
An example of such an optical system is a satellite-borne optical system which involves the use of a metal Vee mirror. This Vee mirror is fabricated in several pieces and, after being aligned to within a fraction of a wavelength of light, must be staked so as to retain the alignment during launch by a rocket. It is also necessary that it be possible to disassemble the optical system without damaging the individual optical components in the event that testing or handling requires disassembly.
U.S. Pat. No. 3,684,380 (Benchley, Jr.) issued on Aug. 15, 1972 discloses a navigational aid comprising two mirrors held at right angles to each other. Benchley suggests attaching the mirrors to a member which is locked to a stud with a threaded rod. This alignment means is not designed to withstand the forces of the launch of a rocket nor is the alignment absolutely critical since the user can adjust his position to correct for deficiencies of alignments. Further, this mirror assembly is designed to be pivotable to two planes to compensate for rough sea conditions.
U.S. Pat. No. 3,832,040 (Ciabrini) issued on Aug. 27, 1974 discloses an optical component mount which utilizes a plurality of thin elastic strips distributed at equal intervals about a universal ball-joint centered on the axis of the optical component. This arrangement is designed to limit the stress placed on the optical component by the mounting means. The elasticity of the flat beams reduces the radial forces at the points of connection to the optical or other element. However, certain radial forces will still exist because of the variance within the dimensional tolerances of fabricated parts.
U.S. Pat. No. 4,037,944 (Hanson) issued on July 26, 1977 discloses a low stress optical mounting structure and method. A mounting bore is formed to loosely receive a mounting post. Lateral bores intersect the mounting bore at right angles and filler material is deposited between the mounting bore and the mounting post extending into the lateral bores. This method is not satisfactory for a number of reasons. Chiefly, the fact that alignments depends upon the compressive strength of a relatively large thickness and small area of adhesive is unsatisfactory. Further, the staking material is not prevented from wicking into the contact areas between optical components. This can perturb the alignment when the adhesive material expands upon curing. Also, this joint cannot be disassembled without subjecting the optical components to disruptive forces. Finally, differential expansion of the adhesive material during setting will cause displacement of the optical components since a pin in a cylindrical bore will be displaced radially unless it is perfectly centered. This would be a significant problem in a highly asymmetric arrangement.